I'm sure everyone here who's ever played the original Doom games (1 and 2, not the mods and whatnot) noticed the soundtrack is practically ripping off real songs. This thread will be used to fill in the complete soundtrack and find out which songs are actually original works and which are just taken from other pieces.
Metallica - No Remorse or Master of Puppets (lots of debate on this one)
Pantera - Rise
E1M9 (and all other hidden levels)
AC/DC - Big Gun
Metallica - The Call of Ktulu
Pantera - Regular People
Pantera - Mouth For War
Slayer - Behind The Crooked Cross
Slayer - Silent Scream
(The fourth episode added in The Ultimate Doom reuses the soundtrack from the rest of the game).
If I remember correctly, Doom II reuses some songs throughout the game's 30 maps, so I'm not gonna bother listing these in any order.
Slayer - South Of Heaven
Black Sabbath - After All (The Dead)
Pantera - This Love
Alice In Chains - Them Bones
Alice In Chains - Angry Chair